This invention is related to medical diagnostic ultrasound imaging, and more specifically to methods for estimating motion between composite ultrasound images and recovering Color Doppler values from composite images.
Several extended field of view methods have recently been proposed. See the discussions in Weng U.S. Pat. No. 5, 782,766; Weng U.S. Pat. No. 5,557,286; Hossack U.S. patent application Ser. No. 09/196,986; and Sumanaweera U.S. patent application Ser. No. 09/196,987. The two above-referenced U.S. patent applications are assigned to the assignee of the present invention.
These patent documents disclose several different methods for registering and composing an extended field of view image. In all cases, substantially coplanar images are sequentially acquired as the transducer moves along the patient""s body parallel to the azimuthal direction. Selected ones of these images are compared with one another to provide transducer motion estimates, and these transducer motion estimates and then used to compose portions of multiple ones of the acquired images to form the desired extended field of view.
Weng U.S. Pat. No. 5,782,766 discusses the superposition of images comprising color-coded Doppler velocity or Doppler energy images. In the disclosed system, the motion estimation is performed on a B-mode image, prior to the time the B-mode image is combined with the Color Doppler image. This approach is not well-suited for use in the situation where the Color Doppler image has already been combined with the B-mode image. This is because speckle correlation methods do not operate on Color Doppler images with optimum effectiveness. Color Doppler data, unlike the speckle of B-mode data, are not motion invariant. This limitation may represent a significant disadvantage in some circumstances, for instance in off-line review stations where only the composite B-mode/Color Doppler image is available.
By way of introduction, the preferred methods described below perform extended field of view or 3-D imaging on composite ultrasound images by first extracting the underlying B-mode images from the composite images and then performing image correlation on the extracted B-mode images to estimate motion. After the relative motion vectors have been determined, selected components of the composite images (B-mode, Color Doppler, or composite B-mode/Color Doppler) are registered using the determined motion vectors and then composed to form the desired extended field of view or 3-D image. In this way, extended field of view and 3-D imaging are made possible from composite color ultrasound images (i.e., mixed-mode images).
The foregoing paragraph has been provided by way of introduction only, and is not intended to limit the scope of the following claims.